Here are the things doctors say you should never do — and what to do instead.

1. Drinking fewer than 2 liters of water every day

No matter where you are, make sure you have water on hand. | Tzam/iStock/Getty Images

Drinking when you’re thirsty to stay hydrated is much easier said than done. That’s why health experts recommend drinking 2 liters (about 64 ounces, or 8 cups) of water on average, even though you get some water from other drinks and many of the foods you eat.

2. Staying out of the sun (or staying in it too long)

Be mindful of how long you’re in the sun and take proper precautions. | Fizkes/iStock/Getty Images

This is one of those frustrating and confusing suggestions too many people get wrong. While getting too much sun increases your risk of cancer, not getting enough is also bad for your health. To boost your vitamin D intake, you should spend about 10 to 15 minutes in the sun daily, without sunscreen.

Make sure that if you’re in the sun any longer than that, you wear sunscreen to protect your skin.

Next: When it comes to aging, this could change everything.

3. Having a bad attitude about getting older

Getting older is a natural part of life. | Feverpitched/iStock/Getty Images

Some research suggests that having a negative outlook on aging can increase your risk of dementia and other serious health issues. If you can focus on the positives when thinking about getting older, you’re much more likely to live a long, healthy, and happy life.

Next: This is what happens when you think about dying too much.

4. Constantly thinking about dying

Worrying about death might actually make you die sooner. Constant stress elevates your disease risk and increases your chances of getting sick — but it doesn’t have to be that way. Talking with someone about your anxieties can actually help.

Next: Do your friends keep calling? Here’s how you should respond.

5. Declining invitations from your friends

Maintaining an active social life is extremely important if you want to stay alive. Seniors are more likely to isolate themselves from family and friends, and this can cause issues like depression and early death. If your friends invite you out, go. If they don’t, invite them first.

Next: Have a questionable relationship with sleep? Here’s how much you need.

6. Sleeping less than 6 hours every night

Some might argue, the more sleep you can get the better. | GeorgeRud/iStock/Getty Images

Health experts recommend that people over 65 should try to get between seven and eight hours of sleep every night. Obviously this number will fluctuate depending on a number of factors, but if you consistently sleep less than six hours, you’re putting yourself at risk for a handful of unwanted health issues.

Next: “Everything in moderation” applies to this next forbidden habit.

7. Drinking more than 2 glasses of wine a day

A little bit of alcohol is actually good for you. But the Centers for Disease Control and Prevention warn against having more than a few drinks per day. Specifically, women should typically limit their intake to a single drink, while men can usually get away with a second.

Your doctor can give more specific recommendations for you personally, depending on your health and age.

Next: Most people eat too much of these types of foods.

8. Eating too many doughnuts

Sugar isn’t a good thing. | iStock.com/Ozgur Coskun

Did you know that eating too much sugar can actually kill you? The added sugars present in foods like doughnuts, potato chips, and frozen dinners are probably fine to eat in moderate amounts. Eating massive amounts of sugar every day isn’t good for your heart, your brain, or your hopes of living past 100.

Next: This might be just as bad for you as smoking cigarettes.

9. Sitting for more than 2 hours at a time

Take regular walking breaks. | iStock.com/g-stockstudio

Do you spend extended periods of time sitting? You’re at risk for more serious health problems than just gaining weight. It’s bad for your heart and other muscles, and it’s not hard to reverse this habit. Make it a point to get up and walk around for five or 10 minutes, at least once every hour.

Next: If you’re doing this while sitting, you’re even worse off.

10. Watching TV for more than 2 hours a day

You may need to limit your time in front of the TV. | iStock.com/wikoski

Can watching TV kill you? Maybe. Maybe not. But related to the health problems associated with sitting, sitting for hours in front of a screen can increase your disease risk. It might help if you do other, mentally or physically stimulating activities with the TV on in the background, like cooking or exercising.

Next: While you’re off the couch, you might as well do this.

11. Exercising less than 150 minutes every week

Keep your fitness routine in check. | Fizkes/iStock/Getty Images

You don’t have to spend hours on your feet day in and day out in order to stay fit. The American Heart Association recommends just 150 minutes of exercise weekly — about 30 minutes of activity, five days each week — to maintain optimal health.

Next: Even if you exercise, this other habit will still cut your life short.

12. Eating more calories than you burn

Overeating will only result in weight gain. | FotoCuisinette/iStock/Getty Images

Overeating — regardless of the type of food — increases your risk of some of the country’s deadliest diseases, including heart disease, type 2 diabetes, and cancer. Even if you exercise regularly and eat mostly healthy foods, eating too much still has the potential to lead to an early death.

Next: Grocery shopping? Don’t skip this section of the store.

13. Walking past the produce section at the supermarket

A fruit bowl should be standard in every home. | Wavebreakmedia/Getty Images

Don’t miss out on the many health benefits of produce. Fruits and vegetables contain large amounts of antioxidants and other minerals essential for staying healthy, especially as you get older. Try to have a serving at every meal.

Next: It’s never too late to quit this destructive habit.

14. Smoking cigarettes

This one may be obvious, but is vital to your health. | Terroa/iStock/Getty Images

Cigarettes aren’t just damaging to your lungs. Smoking them regularly also increases your risk of dying from heart disease. Your risk decreases the less you smoke, and even if you’ve been doing it for years, quitting now can still help save your life.

Next: You might be cutting this out of your diet — but you shouldn’t.

15. Avoiding fish and other ‘fatty’ foods

Fish can be a good thing to eat regularly. | Amarita/iStock/Getty Images

People who follow the Mediterranean diet, which includes foods such as fish and nuts, have been shown to live longer and experience lower rates of age-related diseases like dementia. You should monitor your saturated fat intake, but you can be more lenient with your “healthy” fat choices.